As semiconductor devices such as LSI are made with increasingly higher degree of integration, their operating speeds become higher and electronic components are packaged with higher density, it has been increasingly important to dissipate heat generated in the electronic components. Casings for electronic components, for instance, have been made of metals or ceramics having high thermal conductivity, but resin-based materials have recently come into use that provide high degree of freedom in choosing the shape and ease of reducing the size.
For the resin-based material, such resin compositions have been used that comprise a matrix resin and a filler having high thermal conductivity, such as metal, alloy or ceramic, dispersed in the matrix resin.
A composite material having a part of resin replaced with a low-melting point alloy has also been proposed (Japanese Laid-open Patent Publication No. 6-196884). This publication describes that thermal conductivity of molded parts can be increased by molding a mixed powder containing a resin, a low-melting point alloy and a filler at the room temperature, and heating the preform at a temperature at which the low-melting point alloy completely melts so that the filler particles are fixed by the low-melting point alloy for connecting to each other.